1. Field of the Invention
This invention relates to air supported structures and is more particularly concerned with an air supported, multi-wall, insulated structure wherein the inside temperature is maintained at a temperature different from that of outside air.
2. Description of the Prior Art
Air supported structures having a single sheet of polyethylene, polypropylene, nylon, polyester, glass fabric and similar materials are well known. They are frequently reinforced by webbing, cables or rope. The sheet is anchored around its skirt so that an air pressure differential can be maintained between the inside and the outside. A blower is mounted to discharge air under pressure into the envelope thus formed. Sometimes the blower is continuously operated, with an equal amount of air leaking out of the envelope, once inflation is complete. Other blowers operate intermittently. In any event, a small air pressure differential is sufficient to hold up the envelope in an inflated condition because of its light weight.
Double wall air supported structures having two sheets with a dead air space or cavity therebetween to provide insulation, are known. Their insulating properties are not good.
In the patent to Suits, U.S. Pat. No. 2,649,101, the cavity is filled with an insulating material and the air therein is evacuated, causing the sheets to collapse against the insulation, for providing rigid structure. Other patents, such as the patent to Lee, U.S. Pat. No. 3,304,665, Furrer et al. U.S. Pat. No. 3,357,142 and Ming-Yang Chang, U.S. Pat. No. 3,257,481 describe enclosures, each of which is a rigid insulating structure formed by injecting foaming plastic or similar material into the space between the two sheets. These too form rigid structures.
None of these double-walled structures described above, maintain the flexibility of the outer wall, or sheet, as in single walled structures and in none can the insulating material be easily removed for folding the envelope into a compact, portable form for reinflation at a second site. Furthermore, none has provided adequate insulation at sufficiently low weight for the temperature differential desired between inside and outside.
In the past, to the best of our knowledge, air supported structures have usually not been used for refrigerated structures in humid climates, nor have they found general use in extremely cold climates. The reason for this is probably because, sheets of ice will collect on the warm humid side of a wall when the other side of the wall is at a temperature, below freezing, thereby weighing the structure down or breaking off and falling when wind flexed the structure.
The structure of the present invention obviates the problem of the ice sheets and also the problem of providing a readily transportable, inexpensive structure which can be quickly erected and insulated.
In the past, indoor ski slopes, using artificially manufactured snow, have not, to our knowledge, been produced, even though U.S. Pat. No. 3,250,530 does disclose such a structure. The reason is probably due to the high cost of such a large structure with no central supports. The present invention provides a low cost structure which is suitable for the unobstructed spanning of the ski slope area and for maintaining the refrigerated conditions which are necessary in such a building.